The present invention relates to controlled wheel braking systems and more particularly to a controlled wheel braking system which is responsive to wheel lock up. The controlled wheel braking system of the present invention has particular utility in automotive vehicles, trucks, airplanes, tractors and the like.
The greatest deceleration of a vehicle occurs immediately prior to wheel lock up. As the operator of the vehicle increases the fluid pressure in the braking system, and, thus, the force of the brake shoes on the brake drum, vehicle deceleration is increased. When the fluid pressure in the braking system is increased beyond a certain optimum, the vehicle starts to skid thereby decreasing the actual rate of deceleration of the vehicle.
Naturally, it is highly desirable to employ a braking system which allows for optimum deceleration of the vehicle while at the same time prohibits the vehicle from skidding. By providing a system where fluid pressure is decreased at the instant of wheel lock up, the danger of skidding is eliminated and optimum vehicle braking is obtained.
Several types of antilocking vehicle braking systems are known in the art. Typically, the known systems employ electrical means for sensing the braking problems and thereafter activating the control means. Typical examples of these known systems are shown in U.S. Pat. Nos. 3,813,130 to M. Inada; 3,659,904 to F. Stevens; and 3,611,284 to J. Lewis. These systems suffer from a number of disadvantages, one substantial disadvantage being the high cost of manufacturing the systems. Another, and equally significant disadvantage, is that electrical control systems are not dependable over rough as well as smooth road surfaces.
In order to overcome the disadvantages associated with braking systems heretofore known, it would be highly desirable to design a controlled wheel braking system wherein fluid pressure is relieved upon sensing wheel lock up without the need of electrical components. By providing such a system, skidding is eliminated and optimum braking is obtained while manufacturing costs are held to a minimum.
Accordingly, it is the principal object of the present invention to provide an entirely mechanical controlled wheel braking system which is of simple construction, less costly to manufacture and more dependable than previously known systems.
It is a particular object of the present invention to provide a controlled wheel braking system in which the vehicle wheels are prevented from skidding regardless of the fluid pressure applied by the operator.
It is a still further object of the present invention to provide a controlled wheel braking system wherein the optimum rate of deceleration of the vehicle is obtained.
Further objects and advantages of the present invention will be apparent from a consideration of the ensuing disclosure.